喷射混凝土与普通混凝土的力学性能对比研究

Comparative Study on the Mechanical Properties of Shotcrete and Ordinary Concrete

在隧道工程支护中,喷射混凝土支护层对围岩的变形及应力重分布起着决定性作用。喷射混凝土在早龄期的高强度特性是充分发挥其初期支护作用的保证,为了揭示其力学指标随龄期的演化规律,对具有相同配合比的喷射混凝土和普通模筑混凝土试样开展了5种龄期条件下的单轴压缩试验,对比分析了这两种混凝土的抗压强度、残余强度以及弹性模量。结果表明:喷射混凝土的早龄期强度较高,1d龄期的强度即可达到28d强度的60%,而普通混凝土仅为42%;随着龄期的增长,两种混凝土的强度差异均具有不断减小的趋势,弹性模量差异则变化不大;随着龄期的增长,初次破坏后的两种混凝土逐渐具有仍能满足其强度等级要求的残余强度来抵御二次甚至多次破坏的能力,且喷射混凝土所需的龄期更短;此外,二次破坏后喷射混凝土的强度损失率大体上较高,故耐久性更差,且其残余强度与其抗压强度呈现出规律的一致性。

In the support works of tunnel engineering, shotcrete support layer plays a decisive role in the deformation and stress redistribution of surrounding rock.The high-strength characteristic of shotcrete at early age is the guarantee that gives full play to its initial support function.In order to reveal the evolution laws of its mechanical indicators with age, uniaxial compression tests of shotcrete and ordinary concrete specimens with the same mix ratio were carried out under five cuing ages.And the compressive strength, residual strength and elastic modulus of the two types of concrete were compared and analyzed.The results show that: the early-age strength of shotcrete is higher.The strength of shotcrete at 1 d age can reach 60% of which at 28 d age, while ordinary concrete is only 42%.The rapid hydration characteristic of shotcrete has great influence on its early strength development.With the increase of age, the strength difference between the two types of concrete has a decreasing trend, while the difference of elastic modulus is not obvious.After the initial failure, the two types of concrete gradually possess the residual strength which can still meet the requirements of their strength grade to resist secondary or even multiple failures as the age incre ases.And the cuing age of shotcrete is shorter.In addition, the strength loss rate of shotcrete is higher in general, which means its durability is worse than ordinary concrete.And its residual strength after secondary failure is consistent with its compressive strength.